JP3881079B2 - Semiconductor integrated circuit element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor integrated circuit element suitable for use when, for example, devices are connected by an optical transmission line and an optical signal is exchanged to operate the device.
[0002]
[Prior art]
In some cases, an optical signal is used in order to increase the signal transmission / reception speed between apparatuses. Conventionally, as shown in FIG. 12, when data is transmitted as an optical signal from the transmission side apparatus A to the reception side apparatus B, the light emitting element 11 and the light emitting element driving circuit 12 are provided in the transmission side apparatus A, and this light emitting element driving circuit is provided. 12, a drive signal is given from an integrated circuit element 13 serving as a signal source, the drive signal is converted into an optical signal by the light emitting element 11, and the optical signal is transmitted through an optical transmission line 14 made of an optical fiber.
[0003]
The receiving side device B is provided with a light receiving element 15, a photocurrent detection circuit 16, and a semiconductor integrated circuit element 17 for receiving and processing the transmitted signal, and sent from the transmitting side device A side. An operation of receiving a signal and processing the signal is performed.
[0004]
[Problems to be solved by the invention]
Conventionally, in addition to the semiconductor integrated circuit elements 13 and 17, the light emitting element driving circuit 12 and the photocurrent detection circuit 16 are provided separately. In order to store the light emitting element driving circuit 12 and the photocurrent detection circuit 16. There is a disadvantage that it requires space and power consumption is increased. In particular, when an optical transmission line is provided between the devices A and B with a number of channels ranging from several hundred to several thousand channels, a space for storing the light emitting element driving circuit 12 and the photocurrent detection circuit 16 becomes large. This is an obstacle to downsizing the devices A and B.
[0005]
The object of the present invention is to reduce the space for storing the light emitting element driving circuit and the photocurrent detection circuit even if the number of channels between the devices is large, and to integrate the driving circuit, the detection circuit and the integrated circuit for signal processing. Accordingly, an object of the present invention is to provide a semiconductor integrated circuit having a function of reducing the power consumption by eliminating the power related to signal transmission between them.
[0006]
[Means for Solving the Problems]
The semiconductor integrated circuit element of the present invention is a photocurrent detection circuit, one end of a first constant current source whose other end is a light receiving element connection terminal of the light receiving element is connected to one power source, and the source is connected to the other power source The drain and gate of the first MOS transistor are connected to the other end of the first constant current source, and the second MOS transistor having the same polarity as the first MOS transistor has its gate connected to the gate of the first MOS transistor. And the source thereof is connected to the other power supply to form a current mirror circuit with the first MOS transistor .
[0007]
The gate and drain of a third MOS transistor having a polarity different from that of the second MOS transistor are connected to the drain of the second MOS transistor, the source is connected to one power source, and the same polarity as that of the third MOS transistor. Four MOS transistors have their gates connected to the gate of the third MOS transistor to form a current mirror circuit with the third MOS transistor.
[0008]
According to this structure, because the internal incorporating photocurrent detection circuit to the structure of a semiconductor integrated circuit elements constituting the semiconductor integrated circuit device or the signal processing circuit comprising a signal source, received provided in the semiconductor integrated circuit device it is only necessary to connect the light receiving element to an optical element connection terminal.
[0009]
Accordingly, since the semiconductor integrated circuit element and the light receiving element can be configured only with parts, the occupied space can be reduced. Furthermore, an advantage particularly capable of reducing power consumption more be formed on the semiconductor integrated circuit of CMOS structure of the semiconductor integrated circuit photocurrent detection circuit is obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram for explaining the concept of the present invention. In this example, an optical signal is transmitted from the device A to the device B, and the signal received on the device B side is processed.
For this reason, the transmitting apparatus A is provided with the semiconductor integrated circuit element 20 and the light emitting element 11 according to the present invention, and the receiver apparatus B is provided with the light receiving element 15 and the semiconductor integrated circuit element 30 according to the present invention. Between the apparatuses A and B, an optical transmission line 14 made of, for example, an optical fiber is connected via optical connectors 14A and 14B.
[0011]
In the semiconductor integrated circuit element 20 according to the present invention provided in the transmission side apparatus A, a signal source circuit 21 for generating a signal to be transmitted to the reception side apparatus B and a light emitting element driving circuit 22 are formed in the same semiconductor chip. The Further, the semiconductor integrated circuit element 20 is provided with a light emitting element connection terminal 23 connected to the output terminal of the light emitting element driving circuit 22. Therefore, the wiring of the light emitting element 11 is completed by connecting between the light emitting element connection terminal 23 and the power supply terminal 24.
[0012]
On the device B side, a light receiving element 15 and a semiconductor integrated circuit element 30 according to the present invention are provided. The semiconductor integrated circuit element 30 according to the present invention has a signal processing circuit 31, a photocurrent detection circuit 32, and a light receiving element connection terminal 33. The signal processing circuit 31 and the photocurrent detection circuit 32 are formed in the same semiconductor chip. Is done. The light receiving element 15 is connected between the light receiving element connection terminal 33 and the power supply terminal 34 to complete the wiring.
[0013]
The semiconductor integrated circuit element 20 provided in the transmission side apparatus A shown in FIG. 1 has the configuration of the semiconductor integrated circuit element proposed in claim 1 of this application, and the semiconductor integrated circuit element 30 provided in the reception side apparatus B includes The semiconductor integrated circuit device proposed in claim 3 of this application is provided.
FIG. 2 specifically shows the circuit structure of the light emitting element driving circuit 22 and the photocurrent detection circuit 32 provided in the semiconductor integrated circuit elements 20 and 30. In general, a semiconductor integrated circuit has a CMOS structure. Therefore, the case where the light emitting element driving circuit 22 and the photocurrent detection circuit 32 are constituted by CMOS is shown.
[0014]
The light emitting element driving circuit 22 shown in FIG. 2 connects field effect transistors (hereinafter simply referred to as transistors) Q11 and Q12 in a differential manner, and the transistor Q11 is turned on and the transistor Q12 is turned off in order for the light emitting element to be in the extinction state. To maintain the state. The drain of the transistor Q12 is connected to the light emitting element connection terminal 23. A differentially changing signal is applied from the signal source circuit 21 to the gates of the transistors Q11 and Q12. As a result, the transistor Q12 is turned on at the same time as the transistor Q11 is turned off, and a driving current is supplied to the light emitting element 11 to emit light.
[0015]
In this manner, by driving the light emitting element 11 by the differential circuit, the current flowing in the transistor Q11 causes the light emitting element 11 to emit light by simply switching to the transistor Q12. Fast start-up and high-speed operation can be expected. The constant current circuit 25 connected to the light emitting element connection terminal 23 is a constant current circuit provided to allow a constant bias current to flow through the light emitting element 11. That is, when the light emitting element 11 is, for example, a laser diode, this is a circuit for causing the current near the light emission threshold to flow through the laser diode as a bias current and changing the light emission amount by flowing the current through the transistor Q1.
[0016]
Similarly, the photocurrent detection circuit 32 provided on the receiving device B side is also constituted by a CMOS circuit. Transistors Q21 and Q22, Q23 and Q24, and Q25 and Q26 each constitute a current mirror circuit. The feature of the photocurrent detection circuit 32 is that the input impedance is configured to be as small as possible. That is, by reducing the input impedance, the influence of the capacitance C1 existing between the anode and the cathode of the light receiving element 15 and the stray capacitance C2 existing between the light receiving element connection terminal 33 and the common potential point is reduced, and high speed operation is achieved. This is a circuit configuration that enables the above.
[0017]
This circuit operates as a current comparison circuit, and outputs the pulse signal P from the output terminal OUT by comparing the reference current I _th with the current I ₁ flowing through the transistor Q21 = (photocurrent I _in + bias current I _bias ). To do. That is, as shown in FIG. 3A, when the current I ₁ flowing through the transistor Q13 = (photocurrent I _in + I _bias ) exceeds the reference current I _th , the potential of the output terminal OUT rises, and the output terminal OUT is shown in FIG. 3C. A pulse P is output. Although the ratio of the current mirror has been described as 1, the magnification can be provided as necessary.
[0018]
Further, the photocurrent detection circuit 32 shown in FIG. 2 has a manufacturing deviation in the characteristics of the P channel type (Q23, Q24) and the N channel type (Q21, Q22, Q25, Q26) in the transistors Q21 to Q26 used. The circuit is configured as symmetrically as possible so that it is less affected by timing accuracy when a relative deviation occurs due to environmental temperature fluctuations. As a result, the pair property of the current source that flows the constant currents I _th and I _bias and the pair property of the current mirror composed of the transistors Q21 and Q22 and the current mirror composed of the transistors Q25 and Q26 are good, and manufacturing deviation and environment These ratio characteristics are maintained even by temperature fluctuations. Therefore, no adjustment is required, the yield is good, and the accuracy can be stably maintained with respect to the operating environment.
[0019]
4 to 7 show modification examples of the light emitting element driving circuit 22. FIG. 4 shows an embodiment in which the configuration is simplified as compared with the light emitting element driving circuit 22 shown in FIG. In this embodiment, the transistor Q11 operates as a current switch, and the transistor Q12 operates as a variable resistor for setting the value of the drive current flowing through the transistor Q12 to an arbitrary value.
[0020]
The transistor Q11 is turned on only when the light emitting element 11 emits light, and a current flows through the light emitting element 11. Therefore, an advantage that the power consumption can be reduced as compared with the light emitting element driving circuit 22 shown in FIG.
The light emitting element driving circuit 22 shown in FIG. 5 is an effective circuit example when it is desired to lower the power supply voltage. That is, in the circuit shown in FIG. 5, the light emitting element 11 and the transistor Q14 are connected in series between the power supply voltages + V and −V, and the power supply voltages + V and −V are applied to the series circuit including the light emitting element 11 and the transistor Q14. As can be seen from a comparison with FIG. 4, the voltage that can be applied to the transistor Q14 can be made high, which is suitable for high-speed operation.
[0021]
FIG. 6 shows an example of a circuit structure in which the characteristic points of FIGS. 4 and 5 are combined. FIG. 7 shows an example of the simplest circuit structure. This circuit has a feature that it can be easily driven by an inverter of a CMOS circuit, and further has an advantage that an occupied area can be reduced in the IC, and is suitable for the case of multi-channeling.
8 to 10 show modified embodiments of the photocurrent detection circuit 32. FIG. A photocurrent detection circuit 32 shown in FIG. 8 is a circuit example in which the current detection circuit shown in FIG. 2 is simplified. Also in the case of FIG. 8, when the current I ₁ = (I _in + I _bias ) flowing through the transistor Q21 becomes larger than the reference current I _th , the pulse P is output to the output terminal OUT.
[0022]
The example in FIG. 9 is an example in which a resistor can be formed in the IC. Transistors Q21 and Q22 are grounded gate circuits for the purpose of preventing the operating speed from being deteriorated due to the capacitance formed in the light receiving element 15, the stray capacitance, etc. by lowering the input impedance. Transistors Q25 and Q26 can be replaced by resistors. When the transistors Q25 and Q26 are resistors, the output amplitude is small, but the operation can be speeded up and a differential output can be obtained. Also in the case of FIG. 9, when the current I ₁ = (I _in + I _bias ) flowing through the transistor Q21 becomes larger than the reference current I _{th, the} current of the P-channel transistor Q24 increases, and the current increases to the output terminal OUT. The pulse P is output.
[0023]
FIG. 10 shows a case where the reference voltage V _th is used instead of the reference current I _th used in FIGS. In the circuit shown in FIG. 10, the input current I _in is increased by the light, the voltage Vd1 generated in the resistor Rd1 falls below the reference voltage V _th, decreases the current of the transistor Q22 is, the transistor Q23 instead current I ₂ increases, and a pulse P is output to the output terminal OUT due to the increase in the current I ₂ . The transistors Q24 and Q25 may be resistors as in the case of FIG.
[0024]
FIG. 11 shows an embodiment in which a semiconductor integrated circuit element is provided with both a light emitting element driving circuit 22 and a photocurrent detection circuit 32. Reference numeral 40 denotes a semiconductor integrated circuit element including both the light emitting element driving circuit 22 and the photocurrent detection circuit 32.
Each of the semiconductor integrated circuit elements 40 includes a light emitting element connection terminal 23, a light receiving element connection terminal 33, a light emitting element drive circuit 22, and a photocurrent detection circuit 32, and the light emitting element 11 is connected to each light emitting element connection terminal 23. The light receiving element 15 is connected to the light receiving element connection terminal 33, and an optical transmission line 14 such as an optical fiber is connected between the light emitting element 11 and the light receiving element 15 to exchange signals.
[0025]
By preparing semiconductor integrated circuit elements each having, for example, several hundred channels of light emitting element connection terminals 23 and light receiving element connection terminals 33 in each semiconductor integrated circuit element 40, an IC test can be performed by preparing several semiconductor integrated circuit elements. It can be used for transmission of signals between the main test device and the test head of the device.
[0026]
【The invention's effect】
As described above, according to the present invention, since the light emitting element driving circuit 22 and the current detection circuit 32 are respectively housed in the semiconductor integrated circuit element, these circuits are separately provided outside the semiconductor integrated circuit element. There is no need to provide 22 and 32. Therefore, by applying to a configuration in which transmission / reception of multi-channel signals is performed using an optical signal, there is an advantage that the apparatus can be reduced in size and power can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining an embodiment of the present invention.
FIG. 2 is a connection diagram showing a specific example of a main part of the embodiment shown in FIG.
3 is a waveform diagram for explaining the operation of the specific circuit shown in FIG. 2;
4 is a connection diagram illustrating a modification of the light-emitting element driving circuit shown in FIG. 2;
5 is a connection diagram similar to FIG.
6 is a connection diagram similar to FIG.
7 is a connection diagram similar to FIG.
FIG. 8 is a connection diagram showing a modification of the current detection circuit shown in FIG. 2;
9 is a connection diagram similar to FIG.
10 is a connection diagram similar to FIG.
FIG. 11 is a block diagram for explaining a configuration example in the case where a semiconductor integrated circuit element is provided with both a light emitting element driving circuit and a current detection circuit.
FIG.
The block diagram for demonstrating the prior art.
[Explanation of symbols]
A Transmission side device B Reception side device 11 Light emitting element 14 Optical transmission line 15 Light receiving element 20 Semiconductor integrated circuit element 21 Signal source circuit 22 Light emitting element drive circuit 23 Light emitting element connection terminal 30 Semiconductor integrated circuit element 31 Signal processing circuit 32 Photocurrent detection Circuit 33 light receiving element connection terminal

Claims (3)

A first constant current source having one end connected to one power source and the other end serving as a light receiving element connection terminal;
A first MOS transistor having a drain and a gate connected to the other end of the first constant current source and a source connected to the other power supply;
A gate is connected to the gate of the first MOS transistor, a source is connected to the other power supply, and the second MOS transistor has the same polarity as the first MOS transistor and forms a current mirror circuit with the first MOS transistor. A MOS transistor;
A drain and a gate connected to the drain of the second MOS transistor, a source connected to the one power source, a third MOS transistor having a polarity different from that of the second MOS transistor;
A fourth MOS transistor having the same polarity as the third MOS transistor and having a gate connected to the gate of the third MOS transistor, and forming a current mirror circuit with the third MOS transistor;
Comprising a photoelectric current obtained with current optical current is superimposed from the first flowing through the MOS transistor of the first said light receiving element to the current of the constant current source, a pulse signal by comparing the reference current I _th A semiconductor integrated circuit element comprising a detection circuit . A first constant current source having one end connected to one power source and the other end serving as a light receiving element connection terminal;
A first MOS transistor having a source connected to the other end of the first constant current source, a drain connected to the other power source via a first resistor, and a bias voltage Vb applied to the gate;
A differential circuit that operates differentially between a drain voltage of the first MOS transistor and a reference voltage _Vth ;
A semiconductor integrated circuit device comprising a photocurrent detection circuit comprising: The semiconductor integrated circuit device according to claim 2,
A second constant current source having one end connected to the one power source and the other end connected to the source of the second MOS transistor;
A source connected to the other end of the second constant current source, a bias voltage Vb applied to the gate, and a drain connected to the other power source via a second resistor; ,
And the drain voltage of the second MOS transistor constitutes the reference voltage _Vth .

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